The present application is related to vehicle measurement or inspection systems, and in particular, to a vehicle inspection or measurement system configured to utilize one or more displacement sensors to acquire measurement data associated with various components of a vehicle axle as the vehicle moves past a stationary measuring station.
Systems for measuring vehicle properties, such as wheel alignment and associated parameters, are traditionally set up for obtaining measurements to a high degree of accuracy under controlled conditions, such as with the vehicle disposed in a stationary location on a level surface or alignment lift rack. These systems may require the temporary placement of various inclinometers or optical targets on the vehicle wheels, from which data is acquired to determine the various measurements. In general, vehicle wheel alignment measurement procedures require a technician to spend time preparing the vehicle for measurements, acquiring the measurements, and performing adjustments necessary to correct any identified problems. Often, a vehicle brought in to a shop for other services may unknowingly be in need of an alignment service as well. However, unless the service technician and the vehicle owner are willing to spend the time required to prepare the vehicle for measurement and proceed with an alignment measurement process, alignment issues will likely remain undetected and unrepaired.
In response to the recognized need for a way to quickly identify vehicles which may require an alignment service, various quick check or inspection systems have been introduced to the market, such as the Quick Check® System from Hunter Engineering Co. of St. Louis, Mo. These systems provide an operator with the tools and procedures necessary to quickly (in less than three minutes) obtain basic measurements of important vehicle wheel alignment angles, enter vehicle identifying information (such as through a VIN barcode scan), and review vehicle diagnostic information such as battery condition, tire tread depth, and on-board diagnostic messages. If a vehicle quick check or inspection reveals a potential out-of-specification measurement or problem, it can be quickly brought to the attention of the vehicle owner, who may then elect to proceed with a more in-depth vehicle service procedure, such as a full vehicle alignment service.
Often, vehicle quick check or inspection systems require a technician to carry out various tasks during the process, including attachment of optical targets or angle sensors to the wheels of the vehicle, manual measurement of tire tread depths, and the coupling of scanner component to vehicle data ports. In order for the technician to complete these tasks, the vehicle must be stationary for part of the time, such as for the attachment (and subsequent removal) of optical targets or angle sensors. This necessitates establishing a routine or procedure which must be followed by a technician each time a vehicle is brought into the shop for service. During busy times, or when multiple customers are waiting, a technician may not have sufficient time to carry out these routines or procedures for every vehicle, potentially failing to identify vehicles in need of additional services.
Vehicle wheel alignment systems have utilized a variety of techniques for non-contact measurement of vehicle wheel assembly parameters, from which vehicle alignment angles can be determined. For example, by utilizing multiple displacement measurement sensors, displacement measurements between known sensor locations and multiple locations on a stationary vehicle wheel assembly can be measured. Processing the acquired measurements from sensors observing stationary wheels on opposite sides of an axle can identify planes parallel to the wheel assembly surfaces, from which representations of total toe of an axle can be determined. In other configurations, two-dimensional images of a vehicle wheel assembly can be acquired, and image processing algorithms utilized to identify geometric features such as the wheel rim edge, from which a perspective analysis can be performed to determine estimates of the vehicle wheel assembly spatial position and orientation. Alternatively, structured light patterns, such as multiple laser lines, or colored stripes, can be projected onto the wheel assembly surface and observed by an imaging system. Deviations in the projected pattern are analyzed to generate representations of the illuminated surfaces, from which vehicle wheel assembly spatial position and orientation can be estimated. In general, these systems require the vehicle wheel assembly to remain stationary relative to the sensors during the measurement acquisition procedure, but some non-contact measurement systems require either the vehicle wheel assembly or the sensors be rotated about a stationary axis of rotation during the measurement acquisition procedure.
Some systems can acquire measurements as a vehicle wheel assembly is both rotated and translated past the sensors, such as during vehicle travel. For example, using laser displacement sensors to measure a distance between a fixed sensor and various points on vehicle wheel assemblies on opposite sides of a vehicle as the vehicle is driven at a slow speed between the sensors, enables a system to acquire measurement data along horizontal slices across each of the wheel assemblies, from which approximations of the individual wheel assembly spatial orientations can be derived. These types of systems are highly influenced by the speed at which the vehicle travels between the sensors, the angle (straightness) of vehicle travel relative to the sensor observation axis, and changes in steering of the vehicle as it passes between sensors. Measurements acquired from a moving vehicle are useful to provide a vehicle service quick check or audit inspection, capable of identifying vehicles which may be in need of a further, more precise, alignment inspection and/or adjustment.
Accordingly, there would be a benefit to the vehicle service quick check or inspection industry if an increased number of preliminary vehicle measurements could be acquired as the vehicle is driven, such as by a customer, through a field of view associated with a non-contact measurement station, preferably without the need to stop before or after passing the measurement station, to have a technician install or remove wheel-mounted optical targets or angle sensors.
There would be an additional benefit to the vehicle service quick check or inspection industry if the sensitivity of a non-contact measurement station to variations in vehicle speed, steering, and direction of travel could be accounted for or attenuated.